The goals of this research project are to synthesize polynucleotides of known base sequence for the study of DNA-protein and DNA-drug interactions, and to make improvements in the triester synthesis method that will increase the ease, speed, and yield of such syntheses. This is a collaborative effort of the California Institute of Technology and the City of Hope National Medical Center. Past results from these laboratories have included synthesis of lac operator with its natural and symmetrized sequences, pilot syntheses of AATT and CCGG, and syntheses of three different ten-base-pair "linker" polynucleotides bearing restriction enzyme sites for use in plasmid cloning. The specific research goals covered by this application are as follows: 1) Synthesis of small, homogeneous polynucleotides in the four to ten base pair size range, for use in x-ray crystallographic and chemical studies of DNA structure and of the intercalation process with several antibacterial, antimalarial, schistosomicidal, and carcinostatic organic molecules. 2) Synthesis of longer polynucleotides for studies of base-specific DNA-protein interactions. These will include systematic variants of the operator sequence and CAP binding site of the lac operon in connection with the x-ray analysis of the lac repressor-operator complex at Caltech, and preparation of Eco R1 restriction enzyme site and modifications, for use in the x-ray analysis of the Eco R1 restriction and methylase enzymes. 3) Improvement of the triester method of DNA synthesis to facilitate the research outlined above, including simplification of blocking and deblocking steps, and an increase in speed and yield at each step.